Scientists have uncovered that stromatoporoids, which are ancient organisms that helped build reefs, actually survived the Late Devonian extinction—contradicting previous assumptions—and continued to thrive afterward. This discovery gives us a fascinating look at how these creatures adapted to environmental shifts in the past, providing important lessons for the resilience of marine ecosystems and insights that can inform modern conservation strategies.
Are modern coral reefs facing extinction? It’s hard to say, but evidence suggests that some of their ancient relatives managed to survive unforeseen challenges for quite some time.
Researchers from Osaka Metropolitan University have found that ancient reef-building stromatoporoids persisted beyond the Late Devonian mass extinction, continuing to be significant reef developers for many years after scientists thought they had disappeared. This discovery enhances our understanding of how life on Earth responds to environmental changes, highlighting the adaptability and resilience of marine ecosystems.
While corals are the most recognized reef-builders today, various organisms have contributed to reef formation throughout Earth’s history. Among them were the stromatoporoids, which resemble sponges and played a crucial role in reef structures during the Paleozoic era, especially during the Silurian and Devonian periods (approximately 444 to 359 million years ago).
“It was believed that stromatoporoids had disappeared from the role of reef-builders after the Late Devonian extinction,” explained Yoichi Ezaki, a professor at Osaka Metropolitan University’s Graduate School of Science and the lead author of this study.
The Late Devonian extinction was one of five significant extinction events in Earth’s history, dramatically impacting marine life and leading to a drop in the variety of reef-building organisms. In the Carboniferous period (approximately 359 to 299 million years ago), which followed this extinction, no known stromatoporoid reefs existed until now.
By examining fossils from Carboniferous rocks in the Akiyoshi Limestone Group located in southwest Japan, the team identified laminated skeletons featuring layered and pillar-like structures, both characteristics of stromatoporoids.
“Our findings in Japan indicate that stromatoporoids not only survived but also remained key players in reef construction during the Carboniferous, contrary to previous beliefs,” said Ezaki. “We are confident this discovery will change what is taught in classrooms.”
The Akiyoshi Limestone formed atop a seamount in the Panthalassa Ocean from the Mississippian (early Carboniferous) to the middle Permian periods. Stromatoporoids, along with the organism Chaetetes, thrived in the warm, shallow waters of this seamount, benefiting from conditions such as improved ocean circulation, nutrient-rich upwelling, and increased carbonate saturation resulting from global glaciation.
This indicates that unique and isolated oceanic locations like Akiyoshi might have aided the survival of these resilient organisms.
“The isolated Akiyoshi seamount could have hosted a distinctive biological community, potentially creating a ‘Carboniferous Galápagos’ that reveals the complexities of ancient marine ecosystems,” discussed Ezaki.
Over time, increased global cooling and exposure above sea level began to impact the stromatoporoids. Yet, their continued existence in the late Carboniferous implies they adapted to new ecological roles in response to the shifting climate.
The implications of this study underline the potential resilience of certain reef-building organisms within exclusive environments, imparting valuable takeaways for current conservation initiatives.
“Learning how stromatoporoids and other species adapted to survive past environmental and climatic turmoil provides essential insights into how today’s reef ecosystems might cope with ongoing and future climate challenges,” concluded Ezaki.
